Process of making alizarin.



J'OHANN HEINRICH BONER, Ulr LITDWIUE Milt; SILK FE Unrrnn satires Parana ornrcn.

ANILIN AND SODA FABRIK, OF H PROCEsFi OF MAKING ALIZARIN.

Specification of Letters Patent.

Patented April 21, 1908.

Application filed September 9, 1904. Serial No. 223,922.

TonZZ whom it may concern:

I from by-products, which is obtained ac- Be itknown that l, JOiIANN llnmiucn cording to my invention.

BONER, doctorof philosophy and chemist, l

citizen of the Swiss Republic, residing at Ludwigslralen-on-thc-lthme, Bavaria, in the German Empire, have invented new and useful Improvements in Processes oi" Making;

Alizarin, of which the following is a specifi cation. I

My invention consists in the manufacture and production of alizarin in a very pure condition by the direct oxidation of anthra- 'quinone which has hitherto been considered impossible, the only process for the manufacture of alizarin hitherto practiced being to convert the anthraquinone into anthraquinone monosulfoacid and to pnri'y this, and then melt it with caustic alkali in the presence of an oxidizing agent.

I have now discovered that anthracpiinonc can be directly converted into alizarin by direct oxidation, by heating it with a highly concentrated aqueous solution of caustic alkali in the presence of an oxidizing agent. As examples of substances which can be used as oxidizing agents, I mention alkaline chlorates, alkaline nitrates,- sodium chro mate, the superoxids of sodium, barium,

- manganese, and lead and further ferric oxid;

lead oxid and mercury oxid or even atmospheric oxygen.

' The improvements which my invention shows ever the 'old method are twofold. In the first place, I have only to make use of one process to convert the anthraquinone into alizarin, Whereas according to the old method it is necessary to produce and-isolate an in-' ,termediate compound viz. anthraquinone l l r l latter when treated in the above manner yield in the filtrates coloring matters dyein shades of red dill'crcnt from those obtained on dyeing: with the precipitates. Alizarin, as dill'crcntiated from the product of the present invention is not herein claimed.

The following example illustrates the manner in which I prefer to carry out my invention, but I do not limit myself to this exampie. The parts are by weight.

Dissolve from twenty, to thirty, parts of p tassium chlorate in one hundred parts of water, and add three hundred parts of mixed caustic soda and caustic potash and then stir into the mixture one hundred parts of anthraquinonc. Heat and stir the whole (either in an o )en, or in a closed vessel, placed-in an oil about two hundred degrees centigrade, and

continue the heating until the oxidizing ma terial is used up. Dissolve the melt in water and blow an t irough the solution in order to reconvert to anthraquinone the oxanthranolv formed. Precipit-ate the alazarin by the addition of milk ol lime and filter it oil. The

bath) at a temperature ofv El[AFEN-(lN-THE-RIIINE, Gl lltlil'ANY, ASSIGNOR TO BADISCHE .\'-()N-'l\lllC-RIHNE, GERMANY, A CORPORATION.

filtrate contains small quantities of benzoic a'cid. Decompose the recipitate by means of hydrochloric acid, lilter oil the residue from the solution of calcium chlorid and then dissolve the alizarin by means of dilute caustic soda solution, which leaves any anthraquinone undissolved.

I claim:

1. The process of producing alizarin which consists in heating anthraquinon'e with caustic alkali in the presence of an oxidizing agent. 

